The ever-increasing demand for hydraulically operated telescoping crane becomes of greater load lifting capacity and the resulting increases in size of the telescoping booms has created a need for a less massive mechanism for extending and retracting the telescoping boom. In smaller conventional hydraulically operated telescoping booms, the hydraulic cylinders used to extend and retract the movable boom sections are loaded within the base section and within all of the outward moving boom sections except the fly section of the boom, in some cases. As the boom increases in size and in its number of telescoping sections, the weight of this hydraulic cylinder mechanism becomes intolerable and in its conventional form tends to defeat the purpose of increasing the boom size. It is the objective of this invention to deal effectively with this problem, and more particularly to provide a lighter weight extending and retracting cylinder arrangement in the form of a single cylinder whose weight can be concentrated within the base section of the crane boom.
It is a further feature and objective of the invention to provide on the boom base section in concert with the single boom extending and retracting cylinder thereof a latching assembly including independently operable individual spring activated and power retracted latching or locking pins for each movable boom section, so that each such section can be positively and safely locked in the fully extended or fully retracted position relative to the next innermost section of the boom.
A still further object of the invention is to provide a more reliable and more positive extending and retracting mechanism for each individual boom section in proper sequence. This mechanism involves opposite side intermeshing fingers, each pair of which in the extended or active position under spring loading defines a recess for capturing an extending and retracting rigid plate on each individual boom section. The spring-urged fingers are retracted by associated power means to enable the free passage thereover of movable boom sections whose extending and retracting plates do not require capturing in the creation of a particular desired boom configuration.
Another important aspect of the invention resides in a precision guidance system on the movable boom sections at the rearward ends thereof for a sled structure which closely surrounds the single boom extending and retracting cylinder whose rod end is anchored in the base section at the rearward end thereof. The sled structure is equipped with wear pads including inclined pads at its fore and aft ends which can pass over cooperative stepped lands at the rear ends of the movable boom sections during extension or retraction thereof by operation of the single cylinder.
In general, the present invention is characterized by compactness of construction, efficiency and reliability of operation, maximum safety in operation, and overall practicality from a manufacturing standpoint. Various additional features and advantages will be apparent to those skilled in the art during the course of the following detailed description .